The invention relates to an improved metal crib structure for a rocking chair seating plane, provided with means for connecting to other parts, such as chair legs or feet, backrests, arms and footrests, all constituent parts of the armchair. The same applicant has made an application for a Utility Model for a seating plane crib of the above type, constituted by a metal structure comprising: a fixed rectangular frame, comprising a pair of opposite lateral elements and a pair of opposite front and back elements; each of the lateral elements exhibiting an upwardly projecting tab bearing horizontally pivoting bolts; a support frame for the seating plane, pivoted on the fixed frame according to the horizontal axis and oscillating about it through a limited angle; at least two antagonist elastic means for oscillating, mounted between the fixed frame and the seat support frame.
The above-mentioned crib has encountered some drawbacks. Among them is the fact that the elastic means, usually helix springs, are not adaptable to the various weights of different people sitting on the rocking chair, so that if the springs are of a rigidity such as to permit of perfectly rocking a person of 50 kilograms in weight, they cannot be readjusted for a person of twice that weight. It would be absurd to think of substituting the springs merely to account for such a very probable eventuality.
Further, the above rocking chair cannot be used as a fixed armchair, so that its range of use is limited,
Further still, still with respect to the prior art crib, the pivoting means of the frame of the seating plane on the fixed frame have shown themselves to be poorly effective in solving the typical problems of rocking chairs in the prior art: that is, squeaking during use caused by the friction between the bolts and the pivoting seats, which of course can become very irritating to the user.
The main aim of the present invention is therefore to obviate the above-mentioned drawbacks, by providing a crib structure for an armchair, utilizable both as a rocking chair and as a fixed chair, adaptable to persons of different weight, which at the same time greatly reduces operative squeaks and other irritating noises.